An on-site dosimetry audit for high-energy electron beams. (January 2018)

• Record Type: Journal Article
• Authors: de Prez, Leon; Heukelom, Stan; Jansen, Bartel; Jansen, Wim; van de Kamer, Jeroen; van Klink, Wenze; Kok, Elfried; Perik, Thijs; de Pooter, Jacco; Wittkämper, Frits
• Is Part Of: Physics and imaging in radiation oncology. Volume 5(2018)
• Page Start: 44
• Page End: 51
• Publication Date: 2018-01
• Subjects: Absorbed dose to water -- Audit -- Code of practice -- Dosimetry -- Electron beam -- Radiation therapy; Radiotherapy -- Periodicals; Radiation dosimetry -- Periodicals; Cancer -- Imaging -- Periodicals; Oncology -- Periodicals; 615.842
• DOI: 10.1016/j.phro.2018.02.001
• Languages: English
• ISSNs: 2405-6316

Abstract

Abstract: Background and purpose: External dosimetry audits are powerful quality assurance instruments for radiotherapy. The aim of this study was to implement an electron dosimetry audit based on a contemporary code of practice within the requirements for calibration laboratories performing proficiency tests. This involved the determination of suitable acceptance criteria based on thorough uncertainty analyses. Materials and methods: Subject of the audit was the determination of absorbed dose to water, D w, and the beam quality specifier, R 50, dos . Fifteen electron beams were measured in four institutes according to the Belgian-Dutch code of practice for high-energy electron beams. The expanded uncertainty ( k = 2) for the D w values was 3.6% for a Roos chamber calibrated in 60 Co and 3.2% for a Roos chamber cross-calibrated against a Farmer chamber. The expanded uncertainty for the beam quality specifier, R 50, dos, was 0.14 cm. The audit acceptance levels were based on the expanded uncertainties for the comparison results and estimated to be 2.4%. Results: The audit was implemented and validated successfully. All D w audit results were satisfactory with differences in D w values mostly smaller than 0.5% and always smaller than 1%. Except for one, differences in R 50, dos were smaller than 0.2 cm and always smaller than 0.3 cm. Conclusions: An electron dosimetry audit based on absorbed dose to water and present-day requirements for calibration laboratories performing proficiency tests was successfully implemented. It proved international traceability of the participants value with an uncertainty better than 3.6% ( k = 2).